A common roller grinder, such as that disclosed in EP-516 952, consists of two rollers mounted on a shaft each. The shaft is in turn supported by a frame member such that the rollers are placed at a suitable distance from each other. The rollers rotate in opposite directions, towards each other, such that material to be ground is crushed in the gap which is created between the rollers. The rollers are also movable in the horizontal direction, towards and from each other, due to rotation of the frame members to which the shafts of the rollers are connected.
A problem with such roller grinders is that the rollers can be moved in the horizontal direction independently of each other. E.g., when larger material than intended is entered in the gap, the gap is widened since the larger material presses one or both of the rollers outwards, i.e. from each other in the horizontal direction. These independent movements are often off centre, as compared to the exact centre between the two rollers, which can lead to uneven wear of the roller grinder and/or a need for a stronger construction than really necessary, e.g. due to vibrations resulting from the mentioned off centre position. Also, independent movement of the rollers in the horizontal direction can lead to the rollers being located at different vertical levels during operation, the result being that the grinding is not performed at the exact centre between the two rollers but displaced horizontally, since one roller is located at a different vertical level than the other.
One solution to these problems would be to lock the rollers such that they cannot move in the horizontal direction, but that would in turn create larger problems due to the lack of flexibility relating to the size of the gap between the rollers. Further, such a solution would restrict the possibility of compensating for diameter changes of the rolls caused by wear.